Object Composition in Java

Consider the Employee and Office classes shown below. Which object-oriented design principle is best demonstrated by the relationship between the Office and Employee classes?

public class Employee {
    private String name;
    
    public Employee(String name) {
         this.name = name;
    }
    
    public void work() {
         System.out.println(name + " is working.");
    }
}

public class Office {
    private Employee manager;
    
    public Office(Employee manager) {
         this.manager = manager;
    }
    
    public void startDay() {
         manager.work();
    }
}